Error in Unreal Editor when recompiling MyProject.Managed.dll

[Wyrdplay]

After creating a stock PuzzleSample project and running it. Open the managed project .sln in visual studio 2019 and recompile with a minor change. In my case, I changed the colour materials around just to test the workflow. On returning Unreal Editor to focus is am getting this error, followed by crash reporter.

Entry point exception (UnrealEngine.Runtime): System.Runtime.InteropServices.SEHException (0x80004005): External component has thrown an exception. at UnrealEngine.Runtime.ManagedUnrealTypes.BuildTypes() in C:\dev\MyProject\UE_4.23\Engine\Plugins\USharp\Managed\UnrealEngine.Runtime\UnrealEngine.Runtime\Internal\ManagedUnrealTypes.Builder.cs:line 936 at UnrealEngine.Runtime.ManagedUnrealTypes.Load() in C:\dev\MyProject\UE_4.23\Engine\Plugins\USharp\Managed\UnrealEngine.Runtime\UnrealEngine.Runtime\Internal\ManagedUnrealTypes.Builder.cs:line 72 at UnrealEngine.Runtime.Native.NativeFunctions.OnNativeFunctionsRegistered() in C:\dev\MyProject\UE_4.23\Engine\Plugins\USharp\Managed\UnrealEngine.Runtime\UnrealEngine.Runtime\Internal\Native\NativeFunctions.cs:line 236 at UnrealEngine.Runtime.Native.NativeFunctions.RegisterFunctions(IntPtr registerFunctionsAddr) in C:\dev\MyProject\UE_4.23\Engine\Plugins\USharp\Managed\UnrealEngine.Runtime\UnrealEngine.Runtime\Internal\Native\NativeFunctions.cs:line 120 at UnrealEngine.EntryPoint.DllMain(String arg) in C:\dev\MyProject\UE_4.23\Engine\Plugins\USharp\Managed\UnrealEngine.Runtime\UnrealEngine.Runtime\Internal\EntryPoint.cs:line 80